Municipal Corporation—Limitation on Powers of.—A municipal corporation can exercise only such powers as have been conferred upon it by its charter or by some general law.

Id.—San Francisco — Construction of Tunnel — Assessment District.,—The city and county of San Francisco, although it has power, under section 1 of chapter II of article II of its charter, to construct tunnels, has no power to select any limited area of property within its limits, and impose the cost of the construction of the proposed work upon the owners of such property.

Id.—Cost of Tunnel How to be Paid.—In the absence of a grant of power to assess the cost of an authorized work upon a special assessment district, the expense of the work must be borne by the municipality as a whole, either out of current revenues or by means of a bond issue.

Id.—Change of Grade—Mon-Contiguous Blocks—Tunnel under Intervening Blocks—Assessment for Cost of Work.—Chapter VI of article VI of the charter of that city and county, as amended November 23, 1907 (Stats. Sp. Sess. 1907, p. 41), does not authorize a change of the established grade of two non-contiguous blocks of a specified accepted street, the construction of a tunnel under the intervening blocks, the established grade of which remained unchanged, and the assessment of the cost of the work upon a limited assessment district assumed to be benefited thereby. Such a work is not an exercise of the power to “regrade, repave, sewer, sidewalk, curb or otherwise improve the same so as to conform to such change or modified grade,” within the meaning of section 1 of that chapter. Id.—Assessment District for Cost of Tunnel..—Such chapter does not authorize the creation of an assessment district to bear the cost of constructing the tunnel in or under the portion of the street which remains at its old grade.

Id.—Cost of Work on Accepted Streets.—Assessment to Property-Owners.—The street upon which such work was proposed to be done being an accepted street, the city and county, under sections 8 and 23 of chapter II of its charter, could not impose the cost of improving it in any way authorized by that chapter, to private property-owners, either according to frontage, or by the special assessment district plan.